-<!-- $PostgreSQL: pgsql/doc/src/sgml/ddl.sgml,v 1.62 2006/09/20 01:20:38 neilc Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/ddl.sgml,v 1.63 2006/09/20 21:30:20 tgl Exp $ -->
<chapter id="ddl">
<title>Data Definition</title>
<programlisting>
CREATE TABLE measurement_y2004m02 (
- CHECK ( logdate >= DATE '2004-02-01' AND logdate < DATE '2004-03-01' )
+ CHECK ( logdate >= DATE '2004-02-01' AND logdate < DATE '2004-03-01' )
) INHERITS (measurement);
CREATE TABLE measurement_y2004m03 (
- CHECK ( logdate >= DATE '2004-03-01' AND logdate < DATE '2004-04-01' )
+ CHECK ( logdate >= DATE '2004-03-01' AND logdate < DATE '2004-04-01' )
) INHERITS (measurement);
...
CREATE TABLE measurement_y2005m11 (
- CHECK ( logdate >= DATE '2005-11-01' AND logdate < DATE '2005-12-01' )
+ CHECK ( logdate >= DATE '2005-11-01' AND logdate < DATE '2005-12-01' )
) INHERITS (measurement);
CREATE TABLE measurement_y2005m12 (
- CHECK ( logdate >= DATE '2005-12-01' AND logdate < DATE '2006-01-01' )
+ CHECK ( logdate >= DATE '2005-12-01' AND logdate < DATE '2006-01-01' )
) INHERITS (measurement);
CREATE TABLE measurement_y2006m01 (
- CHECK ( logdate >= DATE '2006-01-01' AND logdate < DATE '2006-02-01' )
+ CHECK ( logdate >= DATE '2006-01-01' AND logdate < DATE '2006-02-01' )
) INHERITS (measurement);
</programlisting>
</para>
<programlisting>
CREATE RULE measurement_insert_y2004m02 AS
ON INSERT TO measurement WHERE
- ( logdate >= DATE '2004-02-01' AND logdate < DATE '2004-03-01' )
+ ( logdate >= DATE '2004-02-01' AND logdate < DATE '2004-03-01' )
DO INSTEAD
INSERT INTO measurement_y2004m02 VALUES ( NEW.city_id,
NEW.logdate,
...
CREATE RULE measurement_insert_y2005m12 AS
ON INSERT TO measurement WHERE
- ( logdate >= DATE '2005-12-01' AND logdate < DATE '2006-01-01' )
+ ( logdate >= DATE '2005-12-01' AND logdate < DATE '2006-01-01' )
DO INSTEAD
INSERT INTO measurement_y2005m12 VALUES ( NEW.city_id,
NEW.logdate,
NEW.unitsales );
CREATE RULE measurement_insert_y2006m01 AS
ON INSERT TO measurement WHERE
- ( logdate >= DATE '2006-01-01' AND logdate < DATE '2006-02-01' )
+ ( logdate >= DATE '2006-01-01' AND logdate < DATE '2006-02-01' )
DO INSTEAD
INSERT INTO measurement_y2006m01 VALUES ( NEW.city_id,
NEW.logdate,
creating a new partition each month, so it may be wise to write a
script that generates the required DDL automatically.
</para>
+ </sect2>
<sect2 id="ddl-partitioning-managing-partitions">
<title>Managing Partitions</title>
<programlisting>
CREATE TABLE measurement_y2006m02 (
- CHECK ( logdate >= DATE '2006-02-01' AND logdate < DATE '2006-03-01' )
+ CHECK ( logdate >= DATE '2006-02-01' AND logdate < DATE '2006-03-01' )
) INHERITS (measurement);
</programlisting>
CREATE TABLE measurement_y2006m02 (LIKE measurement INCLUDING DEFAULTS INCLUDING CONSTRAINTS);
\COPY measurement_y2006m02 FROM 'measurement_y2006m02'
UPDATE ... ;
-ALTER TABLE measurement_y2006m02 ADD CONSTRAINT y2006m02 CHECK ( logdate >= DATE '2006-02-01' AND logdate < DATE '2006-03-01' );
+ALTER TABLE measurement_y2006m02 ADD CONSTRAINT y2006m02 CHECK ( logdate >= DATE '2006-02-01' AND logdate < DATE '2006-03-01' );
ALTER TABLE measurement_y2006m02 INHERIT measurement;
</programlisting>
</para>
<programlisting>
SET constraint_exclusion = on;
-SELECT count(*) FROM measurement WHERE logdate >= DATE '2006-01-01';
+SELECT count(*) FROM measurement WHERE logdate >= DATE '2006-01-01';
</programlisting>
Without constraint exclusion, the above query would scan each of
<programlisting>
SET constraint_exclusion = off;
-EXPLAIN SELECT count(*) FROM measurement WHERE logdate >= DATE '2006-01-01';
+EXPLAIN SELECT count(*) FROM measurement WHERE logdate >= DATE '2006-01-01';
QUERY PLAN
-----------------------------------------------------------------------------------------------
Aggregate (cost=158.66..158.68 rows=1 width=0)
- -> Append (cost=0.00..151.88 rows=2715 width=0)
- -> Seq Scan on measurement (cost=0.00..30.38 rows=543 width=0)
- Filter: (logdate >= '2006-01-01'::date)
- -> Seq Scan on measurement_y2004m02 measurement (cost=0.00..30.38 rows=543 width=0)
- Filter: (logdate >= '2006-01-01'::date)
- -> Seq Scan on measurement_y2004m03 measurement (cost=0.00..30.38 rows=543 width=0)
- Filter: (logdate >= '2006-01-01'::date)
+ -> Append (cost=0.00..151.88 rows=2715 width=0)
+ -> Seq Scan on measurement (cost=0.00..30.38 rows=543 width=0)
+ Filter: (logdate >= '2006-01-01'::date)
+ -> Seq Scan on measurement_y2004m02 measurement (cost=0.00..30.38 rows=543 width=0)
+ Filter: (logdate >= '2006-01-01'::date)
+ -> Seq Scan on measurement_y2004m03 measurement (cost=0.00..30.38 rows=543 width=0)
+ Filter: (logdate >= '2006-01-01'::date)
...
- -> Seq Scan on measurement_y2005m12 measurement (cost=0.00..30.38 rows=543 width=0)
- Filter: (logdate >= '2006-01-01'::date)
- -> Seq Scan on measurement_y2006m01 measurement (cost=0.00..30.38 rows=543 width=0)
- Filter: (logdate >= '2006-01-01'::date)
+ -> Seq Scan on measurement_y2005m12 measurement (cost=0.00..30.38 rows=543 width=0)
+ Filter: (logdate >= '2006-01-01'::date)
+ -> Seq Scan on measurement_y2006m01 measurement (cost=0.00..30.38 rows=543 width=0)
+ Filter: (logdate >= '2006-01-01'::date)
</programlisting>
Some or all of the partitions might use index scans instead of
<programlisting>
SET constraint_exclusion = on;
-EXPLAIN SELECT count(*) FROM measurement WHERE logdate >= DATE '2006-01-01';
+EXPLAIN SELECT count(*) FROM measurement WHERE logdate >= DATE '2006-01-01';
QUERY PLAN
-----------------------------------------------------------------------------------------------
Aggregate (cost=63.47..63.48 rows=1 width=0)
- -> Append (cost=0.00..60.75 rows=1086 width=0)
- -> Seq Scan on measurement (cost=0.00..30.38 rows=543 width=0)
- Filter: (logdate >= '2006-01-01'::date)
- -> Seq Scan on measurement_y2006m01 measurement (cost=0.00..30.38 rows=543 width=0)
- Filter: (logdate >= '2006-01-01'::date)
+ -> Append (cost=0.00..60.75 rows=1086 width=0)
+ -> Seq Scan on measurement (cost=0.00..30.38 rows=543 width=0)
+ Filter: (logdate >= '2006-01-01'::date)
+ -> Seq Scan on measurement_y2006m01 measurement (cost=0.00..30.38 rows=543 width=0)
+ Filter: (logdate >= '2006-01-01'::date)
</programlisting>
</para>